Gem grinding machine

ABSTRACT

A MACHINE ARRANGED TO ELIMINATE THE HAND WORK IN GRINDING CABOCHONS OF SEMIPRECIOUS GEMS IN WHICH THE SIZE AND SHAPE ARE MECHANICALLY CONTROLLED.

' March 1971 E. G. MARSHALL 3,568,369

GEM GRINDING MACHINE Filed May 1, 1969 .rllllllll .HHH IH I I INVENTOR. aw/Iv 6 Mnesmu ATTORNEY I March 9, 1971 E. G. MARSHALL 3,568,369

- GEM GRINDING MACHINE "Filed May 1, 1969 v I 3 sheets-sheet z 40 47 44 I I 5 18,1 I

I 5- E INVENTOR.

bw/A/ 6. Wes/ma ATTURNEY United States Patent 3,568,369 GEM GRINDING MACHINE Edwin G. Marshall, 209 Crawford, Nogales, Ariz. 85621 Filed May 1, 1969, Ser. No. 820,931 Int. Cl. B24b /16, 17/02 US. Cl. 51-97 4 Claims ABSTRACT OF THE DISCLOSURE A machine arranged to eliminate the hand work in grinding cabochons of semiprecious gems in which the size and shape are mechanically controlled.

BACKGROUND OF THE INVENTION (1) This invention pertains to template controlled grinding machines, and is more particularly directed to a grinding machine for cabochons of semiprecious gems that automatically reproduces the Work in a rapid high production manner.

(2) Heretofore, it required a professional with many years experience and skill to make an accurate cabochon. A great amount of time was required by former methods in laborously making a properly shaped and finished cabochon of acceptable quality.

SUMMARY OF THE INVENTION One of the objects of this invention is to provide an automatic grinding machine to grind agate and other materials up to hardness nine to form cabochons.

Still another object is to provide such a machine which enables the most amateur of rockhounds and collectors to make as accurate a cabochon as a professional with many years experience.

Further, the above machine is the answer to the time problem formerly inherent in the production by hand of cabochons.

And another object is to provide a machine that does away with present hand methods while automatically sizing and shaping the cabochon without skill and care upon the part of the operator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of the grinding machine incorporating the features of this invention.

FIG. 2 is a plan view of the grinding machine shown in FIG. 1.

FIG. 3 is a sectional view on the line 33 of FIG. 1.

FIG. 4 is a fragmentary sectional view on the line 4-4 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As an example of one embodiment of this invention, there is shown a gem grinding machine comprising a base upon which are mounted suitable bearing supports 11 and 12 for the grinding wheel spindle 13 on which is conventionally mounted an appropriate grinding wheel 14 being driven by a motor, not shown, through the belt 14a and pulley 14b. A template and work support arm 15 has integral lin'k pieces 16 which have their outer ends pivotally mounted to swing about the axis 17 about the pins 18 carried in the outer ends of the brackets 19 of the feed frame 20 which in turn is pivotally mounted to swing about the axis 21 on the support column 22 fixed on the base 10. A tension spring 23- interconnected between the base 10 and a bracket 19 of the feed frame 20 normally yieldingly swings the pivot axis 17 toward the periphery 24 of the grinding wheel 14 about the axis 21 as indicated by the arrow 25.

The swinging arm 15 is arranged to swing back and forth about the axis 17 by a drive motor 26 having an output shaft 27 to which is fixed a crank arm 28 having a crank pin 29 to which is pivotally mounted one end of an adjustable connecting rod 30, the other end of which is pivotally mounted on a pin 31 fixed in the upper link piece 16 of the swinging arm 15 so that when the motor 26 is energized the swinging arm will rock back and forth about axis 17 as indicated by the arrows 32 between the full line position -15 and the broken line position 15a, best shown in FIG. 4.

A work spindle 33 is journaled in suitable bearings 34 in the swinging arm 15 and is adapted to chuck a shank 35 of the dop 36 upon which the stone 37 to be ground is mounted by suitable adhesive 38. Above the work spindle, and in parallel relationship with it, is journaled the master spindle 39 on suitable bearings 39a in the swinging arm 15. A master cabochon 40, preferably made of metal, has its shank 41 chucked in the spindle 39. Both of the spindles 33 and 39 are synchronously rotated by an appropriate drive motor 41 suitably mounted on the swinging arm 15 and having an output shaft 42 with a sprocket 43 driving a chain 44 operating over the sprockets 45 and 46 respectively fixed on the master spindle 39 and the work spindle 3 3.

The master cabochon 40 is arranged to engage a wear plate 47 on the outer end of the longitudinally adjustable support shaft 48 carried in an appropriate support bracket 49 fixed to the base 10', the longitudinal adjustment and positioning being accomplished by the jamb nuts 50 on the threaded portion 51 of the support shaft 48- and the lug 52 fixed to the base 10. An adjusting screw 58 threaded in the rear of the work spindle 33 adjusts the workpiece stone 37 in against the grinding wheel 14 to thereby regulate the amount ground otf of the contoured surface 54 of the stone 37. The stone 37 at the start of the operation is larger than the master 40 and the stone 37 is held against the grinding wheel periphery 24 by the spring 23 which is just strong enough to hold the stone in contact but not strong enough to overheat and fracture the stone. The master 40 does not contact the wear plate 47 during the grinding of the stone until the stone is ground down to the desired size, whereupon the master contacts the wear plate and prevents further grinding.

What is claimed is:

.1. A gem grinding machine comprising in combination:

(A) a base,

(B) a rotatable grinding wheel mounted on the base,

(C) a feed frame mounted on the base to move relative to a grinding surface of the grinding wheel,

(D) yielding means between the base and the feed frame to normally move the feed frame toward the grinding wheel,

(E) a swinging arm pivotally mounted on the feed frame,

(F) power means interconnected between the swinging arm and the feed frame energizable to rock the swinging arm back and forth on the feed frame,

(G) a work spindle journaled on the swinging arm,

(H) a master Spindle journaled on the swinging arm, the work support relative to the spindle and the grinding (1) power means on the swinging frame including a wheel.

power transmission for rotating the work and master 4. A gem grinding machine as in claim 1 wherein the spindles in synchronism, wear plate is adjustable relative to the base and the master (J) a work support on the spindle to hold the workin the master spindle.

piece in engagement with the grinding surface of the 5 grinding wheel, References Cited (K) a master on the master spindle, UNITED STATES PATENTS (L) and a wear plate on the base arranged to be en- 2 375 620 5/1945 B 51 127 gaged by the master on the master spindle when the 10 1 10/1951 ZL required grinding of the work has been completed. 2. A gem grinding machine as in claim 1 wherein the I I work spindle and master spindle are journaled on parallel TRAVIS MCGEHEE 'Pnmary Exammer axes of rotation. CL XJR' 3. A gem grinding machine as in claim 1 wherein 15 127 adjusting means is provided in the work spindle to move 

